US2602779A - Method of inhibiting hydrogen sulfide corrosion of metals - Google Patents

Description

Patented July 8, 1952 METHOD OF INHIBITING HYDROGEN SULFIDE CORROSION OF METALS Melvin I. Moyer, Lawrence, Kans., and Joseph M. Hersh, Forest Hills, N. Y., assignors to'Cities Service Oil Company, Bartlesville, kla., a corporation of Delaware No Drawing. Original application September 11, 1947, Serial N0. 773,506. Divided and this application May 10, 1949, Serial No. 92,506

Claims.

, 1 Our invention relates to an improved method of inhibiting corrosion of metal, and is more particularly concerned with the treatment of hydrogen sulfide containing brines of the type obtained in the production of crudeoil to reduce their corrosive efiects upon oil production and transmission equipment; o

This application is a division ofour copending application Serial No. '77 3,506, filed September 11, 1947, now U. S. Patent No. 2,496,354.

The corrosive action of oil fieldbrines containing hydrogen sulfide in solution ha long been recognized as a source of very substantial losses in oil production equipment. In some fields, for exampleythe brinewhich is-taken outwith the oil is so corrosive in its nature asto b capable of destroying the well tubing within a matter of a very few months; andthe well casings, separators, pumps, and other equipment with which such mixtures come into contact has a comparably short life. It .has been the practice to utilize caustic soda, soda ash, and other alkaline compounds for neutralizing theacidic components of brines of this general character, and of thereby limiting their corrosive action: These neutralization treatments, however, require the use of comparatively large amounts of the inhibiting agents, are correspondingly costly, and from a long range point of view, have not been outstandingly successful.

The primary object of our invention is to provide an improved process for protecting metals, and particularly iron and steel equipment, used in the handling of crudeoil in the presence of the highly corrosive types of'brines frequently encountered in oil fields.

We have discovered that oil well tubing and casings, as well as other equipment used in oil production, may be sunbstantially and efiectively protected against corrosive action of connate brines by mixing with the latter, an organic amino-reactive compound which serves as a corrosion-inhibitor. In general we have found that the heterocyclic amino-reactive compounds, the alkyl and alkanol amine-aldehyde condensation products of bothcyclic and noncyclic types, and the-alkyl-ureas are effective for our purposes.

In accordance with our invention we inject a suitable quantity of a selectedinhibitor compound into an oil .wellandtherebyimingle it with the oil-brine production sothat the, mixture comes into contact with the well tubing, casing, and other producing equipment. Thus w may duce the inhibitorinto the top of the casing so that it flows down into thewell and thence back through the tubing, pumps, collecting lines, etc. In general we have found that this procedure suflices to protect the entire system of production and collection against corrosion, to a very substantial degree; and far more efiectively than treatment with caustic and other inhibiting compounds which have heretofore been used. While introduction of the inhibitor at the wellhead usually suflices, as has been indicated, it will be obvious that the selected compound may be added to an oil-brine mixture'at any point in a system where its presence is required to limit corrosive, action. It will further be noted that we prefer to introduce the inhibitor, in liquid form, as an aqueous or alcoholic solution for example, for' greater convenience in handling and so that it' may more readily mix with and dissolve in the brine to perform its intended function.

The effectiveness of our inhibitors may be bet-- ter and more easily understood by reference to certain tests which we have conducted upon natural oil field brines containing approximately 40,000 parts per million (by weight) of natural saline solids and about 1,000 parts per million (by weight) of hydrogen sulfide, an analysis. which is typical of corrosive brines produced in many fields. The test procedure involved'the measurement of the corrosive action of this brine, alone and with our inhibitor compounds, upon thoroughly cleaned and polished strip of cold rolled steel measuring! x inches x 16-18 gauge under conditions which closely approximate those existing in a producing oil well. n In carrying out the tests, we filled a series of 16 :ounce bottles with natural gas in order to. exclude. air, and to each added a calculated quantityofone ofiour' amine reactive inhibitors, and then. a measured quantity of brine to ake up the inhibitor mixture, following which ates! strip of known weight was completely immersed'inthe mixture and the bottles were sealed with rubber stoppers to insure an airtight system. .Additional tests were run in other bottles in which the weighed test strips were immersed inzuninhibited brine, that is, in the hydrogen sulfide containing brine just as taken from an oil well. All of the tests were run in multiple, both for the inhibited and the. blank solutions, in order to avoid theanomalies of testing. At the end of a test periodof abouttwo weeks, the

test strips wereremoved from;the-bottles,'rinsed with water, and were then dipped in l; per cent hydrochloric acid solution for ten seconds to remove any light or. acid washable film, following which they weresuccessively rinsed in water, dried and weighed to determine the amount of metal lost in the corrosion treatment.

In several series of tests carried out in the manner describedaboveit was observed that uninhibited corrosion weight loss in different brines varied fromibd'ut' 20mg. to over 170 mg. per test strip while the weight loss of strips subjected to the same brines containing our inhibitors were sharply less. These test data were, used to determine the protection numbers, i. e., the ratio of loss of weight of a strip subjected to an uninhibited brine to the loss of weight, of a strip subjected to the same brine containing our inhibitor, which are reported below in the third column of Table I. For purposes of comparison, we then assumed a weight loss of 100 mg. for the uninhibited strip test, and corrected the actual weight losses suffered by the test strips subjectedto the inhibited brines to this assumed basis, thus give ing the several weight losses set forth in the fourth column or the table.

The results'fofthe'se tests clearly indicate that our. various ihhibitorshave a marked effect in reducing metal loss by the corrosive action of hydrogen sulfide containing brines. Since these tests were. carried out under conditions closely approximating those existing in' actual wells, they demonstrate the inhibiting effect which the agents-have in protecting] oil well tubing, etc.,

under actual producing conditions.

. freeze.

I 3 I Inhibitor lirotee I Weight V Inhibitor j v Ooncention Loss Millia I V- 1 tration Number grams (1 1 nlidgctionproduct of diethanolamine; (2.m01s) and formaldehyde mlllida ction product-of ethylene diamine (1 mol) and formaldehyde R ee it tion product of monoethaiiolaminefd mol) and formaldehydellmoDu It will be observed that the foregoing series of tests were carried out 'in solutions containing 62' -parts-of inhibitor compound per millon parts of brine, thus giving a basis for-evaluating the effectiveness or one' inhibitor with respect to another The protecting effectiveness'of any of these agentsma'y- 'be varied, however, by increasing'or'decreasing the amount employed in the.treating-:process.

' Itimay bernoted that brines taken from different wells,i.eventhough containing about the same concentrationof salt and hydrogen sulfide, maybe; moreor less destructive} in their effects upon oil handling equipment. In using our inhibitors, therefore, we find it desirable to adjust the proportionemployedin accordance with the corrosive character of the brine under treatment. As a generalrule, wefind that fromabout15- to 250parts (by weight) of inhibitonper'million parts"'(by' weight) of brine, is suiiicient to assure highly satisfactory protection under normal op erating conditions. I I

At the conclusion of the foregoingtests, and others which need not be specifically considered, it was observed that the metal strips exposedv to the uninhibited brines were coated with a thin, fiuocculent, raytorblack material. Doubtless this coating has some effect in protecting the underlying metal and slowing down corrosive action. It cannot be of any great protection value, however, because of its tendency to flake off as is evidenced by the fact that the uninhibited brines were turbid with agrayish flocculent precipitate, even lthough they had been standing in'a quiet statefor approximately two weeks. By way of contrast, the metal strips subjected to the brines containing our aminoreactive inhibitors developed thin but highly tenacious coating which appear to be particularly resistant to hydrogen sulfide brine reaction.

' Some; evidence of the resistant character of these films is to beij'found in the fact that a tenminute treatment in 1 per cent hydrochloric acid did not effect complete removal in many cases, and that they were not immediately affected by organic solvents such as alcohol, acetone, ether,

methyl ethyl 'ketone, gasoline, benzene, toluene, carbon tetrachloride,- and similar solvents.

The inhibiting action of the amino-reactive compounds is not fully understood: but one aspect of the action, and thesuccessful protection of metal against substantial corrosion, certainly appears to lie in the formationof a protecting film upon the metal, as described above. These films may be complex organic products developed by the action of the inhibiting agent or its inter-v action with a portion of the hydrogen sulfide and brine, in the presence of metal. They certainly are not the result of mere neutralization of the hydrogen sulfide, as'is evidenced by' the presence of a high concentration .of that ingredient in the treated brines. It may be pos activity of the hydrogen'sulfide, and other cor.-

rosive constituents of the brine. 'Whatever thenature'of the action may be, these facts remain clear: A film is built up on metal surfaces brought into contact with hydrogen sulfide containing brines which have been treated with amino-reactive compounds in accordance with our invention; and those films are resistant both to mechanical abrasion and chemical reaction; and that thepresence of the compounds in such brines doesvery materially inhibit corrosion: of well tubing, casings, and. other oil field equipment carrying the treatedfbrines.

It will be' observed thatv the inhibitor com: pounds are readily obtainable in high concentration, which permits economical shipment and handling both in'transit and in the field.

It is tobe understood that our improved process is not confined to the 'use of only one ofthe inhibiting compounds referred to but the various mixtures of the inhibitors inay be used in a single new and useful'is:

The o ss P v nt n -Pangaea sit-metal x e to We rin s gn ein ng e re ive r, 2 p nd v w h. cempri e n roducing, into thebrine, at thegwell bottom, a.'small;.pro-

portion of diethyl thiourea an'd.thereafter c'ausing the brine Jcontainingth'emethyl-thiourea to flow in contact with the metal surfaces te be pro-' tected. 7 r 2. The process according to claim which diethyl thiourea is incorporated in the brine in'the amount of from about 15 to about 250 parts by weight of diethyl thiourea per million parts by weight of brine.

3. The process of protecting metal equipment which is subject to the corrosive action of oil well brines containing hydrogen sulfide which comprises introducing into a petroleum-brine mixture containing corrosive sulfur compounds. at the well bottom, a corrosion inhibiting agent consisting essentially of diethyl thiourea, and thereafter causing the brine containing the diethyl thiourea to flow in contact with the metal equipment to be protected.

4. The process according to claim 3 in which diethyl thiourea is introduced into the oil in an amount of from about 15 to about 250 parts by weight of diethyl thiourea per million parts by weight of the brine associated with the oil.

5. The process of inhibiting the corrosion of metal equipment when exposed to corrosive brines containing hydrogen sulfide, which comprises introducing into the brine, at the well bottom, a

6 small proportion of diethyl thiourea, the proportion of diethyl thiourea being efiective to substantially inhibit the corrosion of metal equipment, and thereafter causing the brine containing the diethyl thiourea to flow in contact with the metal equipment to be protected.

MELVIN I. MOYER. JOSEPH M. HERSH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

Claims (1)

1. THE PROCESS OF PREVENTING CORROSION OF METALS EXPOSED TO OIL WELL BRINES CONTAINING CORROSIVE SULFUR COMPOUNDS WHICH COMPRISES INTRODUCING INTO THE BRINE, AT THE WELL BOTTOM, A SMALL PROPORTION OF DIETHYL THIOUREA, AND THEREAFTER CAUSING THE BRINE CONTAINING THE DIETHYL THIOUREA TO FLOW IN CONTACT WITH THE METAL SURFACES TO BE PROTECTED.